Effect of Al(Oh)3 particle size on microstructures and strengths of porous MgAl2O4 ceramics

Porous MgAl2O4 ceramics were prepared via in-situ decomposition pore-forming (ISDP) technique using Al(OH)3 and magnesite as raw materials. The influence of Al(OH)3 particle size (0–44 µm, 44–88 µm, 88–100 µm, 100–150 µm) on the microstructures and strengths of porous spinel ceramics were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The bimodal distributions were observed among all the pore size distributions of the porous spinel ceramics. The small pores existed inside the particles and the big pores existed between the particles. When the Al(OH)3 particle size decreased from 100–150 µm to 0–44 µm, the peak of large pores shifted towards left while intensity of the peak of small pores decreased. Simultaneously, the neck-bonds formed between particles grew significantly, which resulted in the increase of compressive strength from 1.4 to 10.8 MPa. The optimized product is the sample with the Al(OH)3 particle size of 0–44 µm, which has a high apparent porosity (55.2%), a high compressive strength (10.8 MPa) and a relatively homogeneous pore size distribution.